Once upon a time, even before the Cookie Monster, there were Bruce and Carole Hart. The couple helped write the 1969 pilot and the early Sesame Street shows that transformed children's TV. Later the Harts collaborated on Mario Thomas' feminist TV special for young people, Free to Be...You and Me. This week their new NBC series for teenagers, Hot Hero Sandwich, is scheduled to debut, exploring with showbiz flash and street corner savvy the problems of adolescence.

The irony is that two people who have been such effective surrogate parents to millions have no children of their own after 16 years of marriage.

"We've been tempted," says Carole, 36. "But, as sensitive as I am to the problems of growing up, I find the idea of being a parent somewhat overwhelming. I don't know that I would be able to make the right decisions. And there would be no room in the kind of schedule we have to parent in a responsible manner. It would be unfair."

Bruce, 41, adds a more pragmatic reason: "In order to free-lance, we had to be able to say 'no' to money, so we could work on what we wanted. It would have been different with children."

Both Harts got into children's programming—and TV in general—as an afterthought. Bruce, son of a Water-town, N.Y. movie theater manager, wrote musicals while majoring in American studies at Syracuse University, then went on to Yale Law School. (He has never practiced law, however, except during a three-year Navy tour.) At Yale, he continued writing songs and jokes for TV comics, which often brought him to New York. He met Carole there.

She grew up in Teaneck, a New Jersey suburb; her dad is an accountant. To support herself while she majored in philosophy at Barnard, she worked as secretary for film director Frank (Diary of a Mad Housewife) Perry. "I was taking a class called 'Theory of Action,' " she recalls. "We were discussing whether raising your hand to get attention was a truly voluntary action. I was so bored I didn't care about raising my hand but I could as a voluntary act get up and walk out and never come back, which I did."

Perry put her in touch with a firm that created multimedia seminars. Carole ended up directing such challenging projects as a one-day review of the history of Western thought for IBM.

She was practicing piano at a friend's house one day in 1962 when Bruce called to ask the woman out. Carole took the call and—since the friend wasn't home—the date, too. Though she soon left for a year of language study in France, their courtship continued by mail. When she returned to Paris after a Christmas visit to the States that included a trip to Vermont with Bruce, he called with a transatlantic proposal.

"In a very confused conversation, he asked me to marry him," Carole says. "He understood that I was saying 'yes' but I really wasn't. Next thing I knew I got phone calls from all my family and they were excited. I thought, 'Oh, the hell with it; this is the kind of decision you never know about anyway.' "

They were married in 1963 and have lived in Manhattan ever since. Bruce landed a job writing for Candid Camera in 1966. When Carole's multimedia project was finished, she wrote freelance until 1968 when she read about plans for Sesame Street. Not long after, she ran into Children's Television Workshop producer Jon Stone at a party and landed a job.

Although Bruce's Candid Camera experience had not made him a TV fan, Carole persuaded him to collaborate on some scripts. By 1970 the Harts had won an Emmy as part of the Sesame Street writing staff. Carole, with Mario Thomas, earned another Emmy in 1974 for co-producing Free to Be...You and Me. Mario finds the Harts "a dream couple to creative people. Their relationship feeds their work and their work feeds their relationship."

The Harts produced a series of educational films for Psychology Today in 1970 but otherwise have been largely pigeonholed as not ready for prime time. Still, in 1978 they wrote, produced and directed an adult TV movie for NBC, Sooner or Later, which aired last March. For Bruce, the film was a breakthrough of another kind. Though he had co-written the words to the Sesame Street theme, he had no real hits to his credit until singer Rex Smith recorded You Take My Breath Away from the movie score. It made the charts this summer.

Hot Hero Sandwich (named for the cafe that is the show's main set) was an offer they would have been foolish to turn down. NBC gave them almost total writing and producing control. "It was just irresistible," Carole says. The program blends skits, songs and interviews with stars about their own problems as teenagers. Olivia Newton-John recalls a teacher who took a particular interest in her. CHIPs star Erik Estrada talks about his parents, and Donna Pescow, in a reaction to her parents' divorce, describes hitting her mother.

Bruce concedes that Carole "interacts with children more than I. She has a way of dealing with young people on their level. There is no patronizing."

She is not always so compatible with adults, he adds: "She is very tough to work with. She wants to make sure all the i's are dotted and all the t's are crossed. Under time pressure, you want to think whatever comes out of your pen is perfect. Carole is able to say, 'I know about the time pressure. This isn't good enough. Do it again.' She can say that a lot."

Usually the Harts divide their work informally; when they disagree, Bruce says, it's "about priorities—what we should be doing first."

They structure their day to minimize conflict. "We have a deal in the mornings," says Bruce. "I make the coffee and get her up. Then we don't talk for an hour, or she tends to be cranky and irritable." When a problem does arise, he admits, "I am a very stubborn son of a bitch. But there's rarely yelling and screaming—maybe three times in our marriage."

When the first package of Hot Hero is completed in February, the Harts plan to switch over to another TV movie; they haven't chosen a subject yet, except that it won't be aimed at children. They have other plans, too. Bruce wants to write "songs, films, plays, etc.," read and relax. "I haven't seen a movie in six months," he says.

They agree that, having achieved economic and professional independence, the idea of having babies seems more appealing. But they approach it as they do everything concerning children—with utmost seriousness. "Up until now, I think we've made the right decision," Bruce says. "But the question is still open. February will probably be a time for discussing that, too." Almost cautiously, Carole adds, "If it is something Bruce feels strongly about, I certainly would have to consider it."